Android update activity UI from service

Question

I have a service which is checking for new task all the time  If there is new task  I want to refresh the activity UI to show that info   I did find https   github com commonsguy cw-andtutorials tree master 18-LocalService  this example  Is that a good approch   Any other examples   Thanks

User · Accepted Answer

See below for my original answer - that pattern has worked well, but recently I've started using a different approach to Service/Activity communication:

Use a bound service which enables the Activity to get a direct reference to the Service, thus allowing direct calls on it, rather than using Intents.
Use RxJava to execute asynchronous operations.
If the Service needs to continue background operations even when no Activity is running, also start the service from the Application class so that it does not get stopped when unbound.

The advantages I have found in this approach compared to the startService()/LocalBroadcast technique are

No need for data objects to implement Parcelable - this is particularly important to me as I am now sharing code between Android and iOS (using RoboVM)
RxJava provides canned (and cross-platform) scheduling, and easy composition of sequential asynchronous operations.
This should be more efficient than using a LocalBroadcast, though the overhead of using RxJava may outweigh that.

Some example code. First the service:

public class AndroidBmService extends Service implements BmService {

    private static final int PRESSURE_RATE = 500000;   // microseconds between pressure updates
    private SensorManager sensorManager;
    private SensorEventListener pressureListener;
    private ObservableEmitter<Float> pressureObserver;
    private Observable<Float> pressureObservable;

    public class LocalBinder extends Binder {
        public AndroidBmService getService() {
            return AndroidBmService.this;
        }
    }

    private IBinder binder = new LocalBinder();

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        logMsg("Service bound");
        return binder;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return START_NOT_STICKY;
    }

    @Override
    public void onCreate() {
        super.onCreate();

        sensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
        Sensor pressureSensor = sensorManager.getDefaultSensor(Sensor.TYPE_PRESSURE);
        if(pressureSensor != null)
            sensorManager.registerListener(pressureListener = new SensorEventListener() {
                @Override
                public void onSensorChanged(SensorEvent event) {
                    if(pressureObserver != null) {
                        float lastPressure = event.values[0];
                        float lastPressureAltitude = (float)((1 - Math.pow(lastPressure / 1013.25, 0.190284)) * 145366.45);
                        pressureObserver.onNext(lastPressureAltitude);
                    }
                }

                @Override
                public void onAccuracyChanged(Sensor sensor, int accuracy) {

                }
            }, pressureSensor, PRESSURE_RATE);
    }

    @Override
    public Observable<Float> observePressure() {
        if(pressureObservable == null) {
            pressureObservable = Observable.create(emitter -> pressureObserver = emitter);
            pressureObservable = pressureObservable.share();
        }
         return pressureObservable;
    }

    @Override
    public void onDestroy() {
        if(pressureListener != null)
            sensorManager.unregisterListener(pressureListener);
    }
}

And an Activity that binds to the service and receives pressure altitude updates:

public class TestActivity extends AppCompatActivity {

    private ContentTestBinding binding;
    private ServiceConnection serviceConnection;
    private AndroidBmService service;
    private Disposable disposable;

    @Override
    protected void onDestroy() {
        if(disposable != null)
            disposable.dispose();
        unbindService(serviceConnection);
        super.onDestroy();
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = DataBindingUtil.setContentView(this, R.layout.content_test);
        serviceConnection = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
                logMsg("BlueMAX service bound");
                service = ((AndroidBmService.LocalBinder)iBinder).getService();
                disposable = service.observePressure()
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(altitude ->
                        binding.altitude.setText(
                            String.format(Locale.US,
                                "Pressure Altitude %d feet",
                                altitude.intValue())));
            }

            @Override
            public void onServiceDisconnected(ComponentName componentName) {
                logMsg("Service disconnected");
            }
        };
        bindService(new Intent(
            this, AndroidBmService.class),
            serviceConnection, BIND_AUTO_CREATE);
    }
}

The layout for this Activity is:

<?xml version="1.0" encoding="utf-8"?>
<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    >
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="com.controlj.mfgtest.TestActivity">

        <TextView
            tools:text="Pressure"
            android:id="@+id/altitude"
            android:gravity="center_horizontal"
            android:layout_gravity="center_vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

    </LinearLayout>
</layout>

If the service needs to run in the background without a bound Activity it can be started from the Application class as well in OnCreate() using Context#startService().

My Original Answer (from 2013):

In your service: (using COPA as service in example below).

Use a LocalBroadCastManager. In your service's onCreate, set up the broadcaster:

broadcaster = LocalBroadcastManager.getInstance(this);

When you want to notify the UI of something:

static final public String COPA_RESULT = "com.controlj.copame.backend.COPAService.REQUEST_PROCESSED";

static final public String COPA_MESSAGE = "com.controlj.copame.backend.COPAService.COPA_MSG";

public void sendResult(String message) {
    Intent intent = new Intent(COPA_RESULT);
    if(message != null)
        intent.putExtra(COPA_MESSAGE, message);
    broadcaster.sendBroadcast(intent);
}

In your Activity:

Create a listener on onCreate:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    super.setContentView(R.layout.copa);
    receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String s = intent.getStringExtra(COPAService.COPA_MESSAGE);
            // do something here.
        }
    };
}

and register it in onStart:

@Override
protected void onStart() {
    super.onStart();
    LocalBroadcastManager.getInstance(this).registerReceiver((receiver), 
        new IntentFilter(COPAService.COPA_RESULT)
    );
}

@Override
protected void onStop() {
    LocalBroadcastManager.getInstance(this).unregisterReceiver(receiver);
    super.onStop();
}

User · Answer

I would recommend checking out Otto  an EventBus tailored specifically to Android  Your Activity UI can listen to events posted on the Bus from the Service  and decouple itself from the backend

User · Answer

Clyde s solution works  but it is a broadcast  which I am pretty sure will be less efficient than calling a method directly  I could be mistaken  but I think the broadcasts are meant more for inter-application communication   I m assuming you already know how to bind a service with an Activity  I do something sort of like the code below to handle this kind of problem   class MyService extends Service       MyFragment mMyFragment   null      MyFragment mMyOtherFragment   null       private void networkLoop                            received new data for list          if myFragment    null              myFragment updateList                                      received new data for textView         if myFragment   null              myFragment updateText                            received new data for textView         if myOtherFragment   null              myOtherFragment updateSomething                           class MyFragment extends Fragment        public void onResume             super onResume             Assuming your activity bound to your service         getActivity   mMyService mMyFragment this             public void onPause             super onPause             Assuming your activity bound to your service         getActivity   mMyService mMyFragment null             public void updateList             runOnUiThread new Runnable                 public void run                       Update the list                                       public void updateText              as above          class MyOtherFragment extends Fragment                public void onResume             super onResume             Assuming your activity bound to your service         getActivity   mMyService mMyOtherFragment this             public void onPause             super onPause             Assuming your activity bound to your service         getActivity   mMyService mMyOtherFragment null             public void updateSomething      etc          I left out bits for thread safety  which is essential  Make sure to use locks or something like that when checking and using or changing the fragment references on the service

User · Answer

I would use a bound service to do that and communicate with it by implementing a listener in my activity  So if your app implements myServiceListener  you can register it as a listener in your service after you have bound with it  call listener onUpdateUI from your bound service and update your UI in there

User · Answer

for me the simplest solution was to send a broadcast  in the activity oncreate i registered and defined the broadcast like this  updateUIReciver is defined as a class instance      IntentFilter filter   new IntentFilter      filter addAction  com hello action       updateUIReciver   new BroadcastReceiver                   Override             public void onReceive Context context  Intent intent                      UI update here                            registerReceiver updateUIReciver filter     And from the service you send the intent like this   Intent local   new Intent     local setAction  com hello action     this sendBroadcast local     don t forget to unregister the recover in the activity on destroy    unregisterReceiver updateUIReciver

User · Answer

Callback from service to activity to update UI  ResultReceiver receiver   new ResultReceiver new Handler          protected void onReceiveResult int resultCode  Bundle resultData              process results or update UI          Intent instructionServiceIntent   new Intent context  InstructionService class   instructionServiceIntent putExtra  receiver   receiver   context startService instructionServiceIntent

User · Answer

My solution might not be the cleanest but it should work with no problems  The logic is simply to create a static variable to store your data on the Service and update your view each second on your Activity   Let s say that you have a String on your Service that you want to send it to a TextView on your Activity  It should look like this  Your Service    public class TestService extends Service       public static String myString              Do some stuff with myString   Your Activty   public class TestActivity extends Activity       TextView tv       Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           tv   new TextView this           setContentView tv           update            Thread t   new Thread                  Override             public void run                     try                       while   isInterrupted                              Thread sleep 1000                           runOnUiThread new Runnable                                  Override                             public void run                                     update                                                                                                      catch  InterruptedException ignored                                      t start            startService new Intent this  TestService class              private void update                update your interface here         tv setText TestService myString

[android] Android update activity UI from service

Examples related to android